梭曼引起大鼠神经肌接头突触后膜持续性去极化的机制

Mechanism underlying the sustained depolarization of neuromuscular junction induced by soman in rats

目的 研究梭曼引起神经肌接头突触后膜持续性去极化 (SD)的产生机制。方法 不均匀牵张肌肉标本上 ,采用传统的微电极细胞内记录技术。结果 随着梭曼浓度 ( 3 0～ 0 0 5 ) μmol L的降低 ,在其所引起的SD过程中 ,小终板电位 (mEPP)的出现逐渐提前 ,并且频率也逐渐增高。当梭曼浓度降到 0 0 5 μmol L时 ,在SD的平台期、复极期及复极后的一段时间内出现频率显著增高的mEPP。反复给予膈神经短暂的串刺激或给予一个长时程的串刺激 ,当刺激落到SD的复极期 ,均可产生小幅度的终板电位 (EPP)。结论 梭曼引起的SD过程中 ,突触后膜烟碱受体没有完全失敏 ,SD的产生可能主要与突触前递质释放因素有关。

Objective To study the mechanism underlying the sustained depolarization (SD) of neuromuscular junction induced by soman in isolated non-uniform stretched muscle preparation of rat diaphragm.Methods Using conventional intracellular recording with microelectrodes.Results mEPP appeared earlier and stronger during SD with decreasing of the concentration of soman.When soman applied 15 min at 0.05 μmol/L concentration,high frequency of miniature end-plate potentials(mEPPs)appeared on the plateau of SD,at the repolarization phase of SD and a certain period after SD.Low amplitude EPPs were induced by the train stimulations applied at the repolarization phase of SD.Conclusion Nicotinic acetylcholine receptors on postjunctional membrane were not completely desensitized during SD.Presynaptic effects may be involved in the mechanism underlying the sustained depolarization induced by soman.